PyExpressionEvaluator这个提示啥意思，表示属性未引用吗？

发生时间： 10:57:10
错误编号： PyExpressionEvaluator
错误信息： 表达式计算出错:FReqType = FExpenseItemID.FExpenseType
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调用堆栈：
在 Kingdee.BOS.Scripting.PyExpressionEvaluator.Run(Expression expression, ExpressionContext context)
在 Kingdee.BOS.Business.DynamicForm.BusinessService.Calculate.DoAction(FormBusinessServiceArgs e)
在 Kingdee.BOS.Core.DynamicForm.FormBusinessServiceUtil.ExceuteServices(List`1 sers, DynamicObject activeRow, Int32 rowIndex)
在 Kingdee.BOS.Core.DependencyRules.EntityRule.Execute(BOSActionExecuteContext context)
在 Kingdee.BOS.Core.DependencyRules.RuleContainer`6.Execute(C executeContext, TaskCollection tasks)
在 Kingdee.BOS.Core.DependencyRules.RuleContainer`6.Resume(C executeContext)
在 Kingdee.BOS.Core.DependencyRules.RuleContainer`6.Raise(S arg, C executeContext)
在 Kingdee.BOS.Core.DependencyRules.BOSRuleContainer.RaiseDataChanged(String fieldKey, Object dataEntity, BOSActionExecuteContext executeContext)
在 Kingdee.BOS.Web.DynamicForm.DataBinder.FieldDataChanged(ModelDataChangedEventArgs e)
在 Kingdee.BOS.Core.DynamicForm.ModelDataChangedHandle.Invoke(Object sender, ModelDataChangedEventArgs e)
在 Kingdee.BOS.Core.DynamicForm.AbstractDynamicFormModel.UpdateField(Field field, DynamicObject activeRow, Object value, Int32 rowIndex, Object oldValue)
在 Kingdee.BOS.Core.DynamicForm.AbstractDynamicFormModel.SetValue(Field field, DynamicObject activeRow, Object value, Int32 rowIndex)
在 Kingdee.BOS.Core.DynamicForm.AbstractDynamicFormModel.SetValue(Field field, Object value, Int32 row)
在 Kingdee.BOS.Core.DynamicForm.AbstractDynamicFormModel.SetValue(String key, Object value, Int32 row)
在 Kingdee.BOS.Web.DynamicForm.DynamicWebFormView.DoLookUpSetFieldValue(FieldAppearance ap, ILookUpField lookUpField, Int32 rowIndex, ListSelectedRow selectRow, String combinedFieldKey)
在 Kingdee.BOS.Web.DynamicForm.DynamicWebFormView.DoLookUpAfterShow(String key, Int32 row, ILookUpField lookUpField, FieldAppearance ap, FormResult result, String combinedFieldKey)
在 Kingdee.BOS.Web.DynamicForm.DynamicWebFormView.<>c__DisplayClass4d.b__4c(FormResult result)
在 Kingdee.BOS.Web.DynamicForm.DynamicWebFormView.<>c__DisplayClass36.b__34()